Autofocus (AF) Modes : What is AF-s, AF-c, AI-Servo-DMF?

AUTOMATIC FOCUS OPTIONS

Oh, those mischiefs! Actually, since photography is a universal concept, its language is universal, but … There may be some issues that companies cannot agree on, and the subject of our article is one of them. Canon has given a separate name, Nikon is different; Sony, Pentax and other names … In this article, we discussed topics such as what is af mode in cameras, what is af-s from autofocus modes in cameras, what is af-c, what is af mf. In other words, we will focus on Auto FOCUS MODES (SETTINGS). Or should I say Focus Mode or autofocus (AF) mode …

On one side, this is actually very simple. I’ll tell you soon; AF Mode, Focus Mode or focus mode is what you want to be told about ‘how to focus. What we call Focus Mode is what type of autofocus occurs. There are focus options under Autofocus Menus. We will examine these options.

Types of Focus

First, let’s divide the focus into two parts: 1. Automatic focus (automatic focus – af) and 2. Manual focus (manual focus-mf). In manual focus, focusing on the subject to be photographed is done manually whit hand. There are focus rings on the lenses and we focus on turning these rings to the left and right. Autofocus (on lenses with an autofocus system) is self-focus without the need for anything else when the camera shutter button is pressed halfway. It happens very quickly and provides great convenience.

The main subject of our article will continue on autofocus modes – options. There are 2 types of autofocus options according to their brands, 3 in others, and 4 in some. Let’s briefly explain these 4 options:

1. AF-S (One Shut or Single SERVO) What is autofocus? When should it be used?

In the mentioned option, the focus point of the camera is focusing when the shutter-release button is pressed halfway and locking the focus to this distance. The focus distance never changes until the shutter is released. To choose a new focus point, we need to release the shutter, select the focus point and make a half shutter again.
AF-S, i.e. single-point focus is often used for shooting fixed, stationary subjects. It is very difficult to focus on moving objects in this mode. Pressing and releasing the shutter continuously takes a lot of time as the sharpness will change constantly depending on the movement. It is therefore not recommended for moving objects. Portrait scenery is used for steady object shots.

Focus point selection is also very important in AF-S mode. Because the camera will focus on the point you choose. If the point is in the center, it will focus on the center, and if the focus point is selected at the edges, it will focus on the edge. Likewise, the focus area will also be important. While the location corresponding to the single point you will select in the single point will be focused, if the area is selected, the inside of the selected area will be tried to be focused. Nikon af point selection and Canon af point replacement also differ due to their menus.

2. What is AF-Continuous (AF-C) (AI Servo or Continuous Servo) Autofocus? When should it be used?

In this type of focus, focus does not remain fixed and locked. If the focus point of the camera is on an object, the camera is locked to this subject when a half shutter is made. This object is automatically detected and the machine moves the focus point with this object even if it moves. As with single point focus, the distance is not locked, the subject itself is locked. Focus can change continuously depending on the movement of the subject and continues until the photo is taken.

AF-C breeding should be preferred for shooting objects in motion. Especially for those who act very fast. We should use it at speeds we cannot focus with AF-S.

The accuracy rate of AF-C focus is directly related to the camera. Technological differences, such as processor speed, focus point number or lens amnesty, directly affect the accuracy of focus. It is not easy to focus the moving object. Even the best machines can miss focus from time to time.

3. What is  AI autofocus (AI Focus, AF-A or Auto Continuous Servo)? When should it be used?

In AF-A mode, the camera takes the initiative and decides which of the two options above to use. If I say which AF-S or AF-C is the full autofocus mode the camera chooses to use, it won’t be wrong. Cameras use AF-S mode when they detect a stationary object, and AF-C when they detect a moving object. He decides which one to use. This option may not be available on some cameras.
It is practical to use the AF-A option. However, since all focus control is left on the camera, changing these settings from the menu may take time and cause the picture to be missed. ‘Ai’ mean is intelligent aotofocus.

Let me finish by explaining my own usage style. I mostly use AF-S and I get clarity from the point I choose, I lock and adjust my frame accordingly. I also use AF-S as long as I do not need others since I have witnessed that AF-S gives more stable results. But if I go to a shot where the movement is very intense, I use the AF-C mode.

4. What is DMF (Direct Manual Focus) from Autofocus Modes? When should it be used?

In addition to what I wrote above, let’s explain another AF mode, which is frequently used in mirrorless models. Its long name is Direct Manual Focus. Autofocus works when this option is selected. There is also the possibility to fine-tune the sharpness ring of the lens in the case of a half shutter. It does not allow changing the focus from the focus ring after focusing in the other 3 modes. When the shutter-release button is pressed halfway down, the electronic zoom is made to the selected point automatically when the focus ring is touched (if the camera’s focus magnification settings are on). Thanks to this zoom, it is possible to make very fine adjustment as the object to be focused is approached. It becomes a sort of “autofocus + manual focus”. When the half shutter is released, it will be restored. In addition to being able to be seen from the electronic viewfinder as close to the eye as possible, the DMF can also be inserted into the object a lot. It will provide great convenience to mirrorless machine users.

Let me state it when I think of it; all I write is with lenses with autofocus, and you have to make sure the lens is in AF mode. Otherwise, we will be rowing in vain. Nothing I wrote above will work in any manual lens or manual modes of auto lenses.

Let your light be of good quality …